<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .box{
      display: flex;
    }
    .item{
      /*数值越小排的越靠前*/
      order: 1;
      flex-grow: 1;
      flex-shrink: 1;
      flex-basis: auto;
      /* 0 1 auto*/
      flex: initial;
      /* 1 1 auto*/ 
      flex: auto;
      align-self: flex-start;
      align-self: flex-end;
    }
  </style>
</head>
<body>
  <div class="box">
    <div class="item"></div>
  </div>
  
</body>
</html>